From the Super Mario Wiki
In The Super Mario Bros. Super Show! live-action segment "Cher's Poochie", Cher, having an emergency dimple appointment with her plastic surgeon, decides to leave her dog, Poochie, in the care of Mario and Luigi at Mario Brothers Plumbing.
After leaving Poochie with Mario, Cher is escorted out of the apartment by Luigi, who kept asking her for her autograph - which Cher gave him, on a pizza.
Later, Cher returns to Mario Brothers Plumbing to pick-up Poochie, who, unbeknownst to her, had his body switched with Mario due to a malfunction in his Pizza Transformer. Confused as to why "Mario" is pawing at her, Cher goes over to "Poochie", who causes her to faint due to him talking to her in Mario's voice.
While Cher lays on the floor, unconscious, Luigi attempts to change Poochie and Mario back to normal and uses the Pizza Transformer on them; unfortunately, though Mario gains his body back, Poochie's mind is seemingly transferred into Cher's body, with Cher's mind presumably being put into Poochie's body.